Sigismund of Luxembourg, King of Germany and Holy Roman Emperor-elect, assumes the Bohemian crown after the death on August 16, 1419, of his half-brother Wenceslas, ending decades of arguments and fights over the king’s choice of candidates for higher offices and church reform.

However, the Hussites, who hold the emperor partly responsible for Huss’s execution, will not allow him to take the Bohemian throne.

Zizka, like most Czechs, refuses to acknowledge Sigismund as king of Bohemia even though the latter offers him the viceroyalty of Bohemia.

Sigismund and Pope Martin V join forces to expunge the Hussite heresy and install the new king.

Pierre d’Ailly: Theologian, Church Reformer, and Cosmographer (1395–1418)

Pierre d’Ailly (1351–1420) was one of the most influential theologians and churchmen of his time, playing a pivotal role in resolving the Great Schism (1378–1417) and shaping conciliarist thought. A strong advocate for church unity and reform, he was also a prolific writer on astrology, geography, and ecclesiastical power.

I. D’Ailly’s Role in the Great Schism and Church Reform

• The Western Schism had divided the Church, with multiple rival popes claiming legitimacy.
• D’Ailly was slow to embrace conciliarism but later became a key participant in the major councils seeking to resolve the crisis:
  • Council of Pisa (1409): Attempted to depose the rival popes but inadvertently created a third papal claimant.
  • Council of Constance (1414–1418): Successfully ended the Schism by deposing all competing popesand electing Martin V.
• D’Ailly dominated the early sessions of the Council of Constance, working alongside Jean Gerson to promote reform and the supremacy of a general council over the papacy.

II. His Ecclesiastical Career and Political Influence

• D’Ailly’s theological and political versatility helped him rise through the ranks of the Church:
  • Bishop of Le Puy (1395).
  • Bishop of Noyon (1397).
  • Bishop of Cambrai (1397).
• In 1411, Antipope John XXIII made him a cardinal, earning him the title Cardinal of Cambrai.
• His connections with both the French monarchy and various papal factions made him a valuable mediator during the Schism.

III. Writings on Cosmography, Astrology, and Prophecy

• Imago Mundi (1410):
  • A cosmographical treatise that attempted to synthesize geographical knowledge.
  • Influenced Christopher Columbus, particularly in his estimates of the world’s landmass, contributing to his belief that Asia was much closer to Europe than it actually was.
• Astrology and Free Will:
  • D’Ailly sought to balance divine omniscience with human free will, arguing that astrological influences did not override moral responsibility.
• The Schism and the Apocalypse:
  • He placed the division of the Church within an apocalyptic framework, speculating on whether the Schism was a sign of the coming of the Antichrist.

IV. After the Council of Constance: Return to Paris

• Following the successful resolution of the Schism, d’Ailly returned to Paris, continuing his writings and advisory roles.
• His conciliarist views and support for Church reform remained highly influential, helping shape later debates on the authority of councils versus the papacy.

V. Legacy and Influence

• A leading figure in the Church’s most turbulent period, d’Ailly was instrumental in ending the Great Schism and reinforcing the role of general councils.
• His writings on cosmography influenced early exploration, particularly Columbus’ assumptions about the shape of the world.
• His theological and astrological works reflected a deep engagement with the spiritual anxieties of his time, bridging scholasticism, humanism, and reformist thought.

D’Ailly’s career, spanning church politics, theology, astrology, and cosmography, made him one of the most versatile intellectuals of the late medieval period, shaping both the Church’s political future and the intellectual currents that led to the Age of Exploration.